Interconnect structure and method of forming the same

Abstract

An interconnect structure and a method of forming an interconnect structure are disclosed. The interconnect structure includes a lower etch stop layer (ESL); a middle low-k (LK) dielectric layer over the lower ESL; a supporting layer over the middle LK dielectric layer; an upper LK dielectric layer over the supporting layer; an upper conductive feature in the upper LK dielectric layer, wherein the upper conductive feature is through the supporting layer; a gap along an interface of the upper conductive feature and the upper LK dielectric layer; and an upper ESL over the upper LK dielectric layer, the upper conductive feature, and the gap.

What is claimed is: 
     
       1. A semiconductor device, comprising:
 a first dielectric layer; 
 a second dielectric layer over the first dielectric layer; 
 a third dielectric layer over the second dielectric layer; 
 a first conductive feature in the third dielectric layer; 
 a gap between the first conductive feature and the third dielectric layer, the gap contacting an upper surface and a lower surface of the second dielectric layer, wherein the gap extends under the first conductive feature in a cross-sectional view; and 
 a fourth dielectric layer over the third dielectric layer, the first conductive feature, and the gap. 
 
     
     
       2. The semiconductor device of  claim 1 , wherein the second dielectric layer comprises a first low-k dielectric layer. 
     
     
       3. The semiconductor device of  claim 2 , wherein the third dielectric layer comprises a second low-k dielectric layer. 
     
     
       4. The semiconductor device of  claim 1 , wherein the gap extends completely under the first conductive feature in the cross-sectional view. 
     
     
       5. The semiconductor device of  claim 1 , wherein the second dielectric layer contacts the first conductive feature. 
     
     
       6. The semiconductor device of  claim 1  further comprising:
 a fifth dielectric layer; and 
 a sixth dielectric layer over the fifth dielectric layer, wherein the first dielectric layer is over the fifth dielectric layer, wherein the first conductive feature extends into the fifth dielectric layer. 
 
     
     
       7. The semiconductor device of  claim 6 , wherein the gap extends between the first conductive feature and the fifth dielectric layer. 
     
     
       8. The semiconductor device of  claim 7 , wherein the gap contacts a lower surface of the sixth dielectric layer. 
     
     
       9. A semiconductor device, comprising:
 a first dielectric layer; 
 a second dielectric layer over the first dielectric layer; 
 a third dielectric layer over the second dielectric layer; 
 a fourth dielectric layer over the third dielectric layer; 
 a first conductive feature in the fourth dielectric layer and the third dielectric layer, the third dielectric layer physically contacting the first conductive feature; 
 a second conductive feature in the second dielectric layer extending from the first conductive feature and through the first dielectric layer; 
 a gap between the first conductive feature and the fourth dielectric layer and between the second conductive feature and the second dielectric layer, the gap contacting a surface of the first conductive feature over the third dielectric layer and a surface of the second conductive feature below the third dielectric layer; and 
 a fifth dielectric layer over the fourth dielectric layer, the first conductive feature, and the gap. 
 
     
     
       10. The semiconductor device of  claim 9 , wherein the gap extends under the first dielectric layer. 
     
     
       11. The semiconductor device of  claim 10  further comprising:
 a sixth dielectric layer underlying the first dielectric layer, wherein the gap completely separates the first conductive feature from the sixth dielectric layer. 
 
     
     
       12. The semiconductor device of  claim 9 , wherein the gap has a dielectric constant of 1. 
     
     
       13. The semiconductor device of  claim 9 , wherein the gap has a width in a range from about 1 Å to about 100 Å. 
     
     
       14. The semiconductor device of  claim 9 , wherein the gap contacts opposing surfaces of the third dielectric layer. 
     
     
       15. A semiconductor device, comprising:
 a first dielectric layer; 
 a second dielectric layer over the first dielectric layer; 
 a third dielectric layer over the second dielectric layer; 
 a first conductive feature extending through the third dielectric layer and the second dielectric layer and into the first dielectric layer, the second dielectric layer physically supporting the first conductive feature, an air gap contacting a first sidewall surface of the first conductive feature above the second dielectric layer and extending between the first sidewall surface of the first conductive feature and the third dielectric layer, the air gap further contacting a second sidewall surface of the first conductive feature below the second dielectric layer and extending between the second sidewall surface and the first dielectric layer; and 
 fourth dielectric layer over the first conductive feature and the third dielectric layer. 
 
     
     
       16. The semiconductor device of  claim 15  further comprising:
 a second conductive feature; and 
 a fifth dielectric layer over the second conductive feature, wherein the first conductive feature extends through the fifth dielectric layer to the second conductive feature. 
 
     
     
       17. The semiconductor device of  claim 16 , wherein the air gap contacts an upper surface of the fifth dielectric layer. 
     
     
       18. The semiconductor device of  claim 17 , wherein the fifth dielectric layer contacts the first conductive feature. 
     
     
       19. The semiconductor device of  claim 15 , wherein the air gap extends along a bottom surface of the first conductive feature. 
     
     
       20. The semiconductor device of  claim 15 , wherein the air gap has a width in a range from about 1 Å to about 100 Å.